If iPhone Screen Dims Randomly with auto-brightness disabled, you should be able to fix the problem by disabling certain other auto-display features as provided below in this article.
iPhone Screen Dims Randomly
While the most common reason for iPhone screen dimming randomly is Auto-Brightness, there are certain other display features that can make iPhone screen to automatically change its brightness level.
For example, display features like True Tone, Night Shift Mode and Reduce White Point can make the display appear less bright or Dim due to surrounding lighting condtions.
Also, if you are located in a place without air conditioning, iPhone automatically dims the screen brightness to prevent your device from becoming hot.
1. Disable True Tone
The True Tone feature is enabled by default on iPhone and its main function is to automatically adjust the intensity of the display, based on surrounding lighting conditions.
Apart from this, True Tone automatically changes the color display on your device, in an effort to make the images appear more natural.
Hence, disable the default True Tone feature on your device and see if this helps in fixing the screen dimming problem on your iPhone.
Go to Settings > Display & Brightness > Move the toggle next to True Tone to OFF position.
2. Disable Night Shift Mode
Another common reason for iPhone screen dimming automatically is due to Night Shift Mode being enabled on the device.
Go to Settings > Display & Brightness > Night Shift > move the toggle next to Scheduled and Manually Enabled Until Tomorrow to OFF position.
Note: According to Apple, Night Shift Mode may help you get better sleep.
3. Disable White Point
While, Reduce White Point feature is designed to reduce the intensity of bright colors on iPhone screen, in certain conditions it can make the screen appear less bright or dim.
Go to Settings > Accessibility > Display & Text Size > move the toggle next to Reduce White Point to OFF position.
Note: If your iPhone is set to high brightness level, switching OFF Auto-Brightness can have an impact on Battery Life.
4. Disable Attention Aware Feature
While Attenntion aware features are designed to dim the screen of iPhone while you are not looking at it, they can also end up dimming the screen while you are actually using your device.
Go to Settings > Face ID & Passcode > move the toggle next to Attention Aware Features to OFF position.
Once Attention Aware Feature is disabled, you won’t find the screen of your iPhone dimming automatically.
5. Switch OFF Music
iPhone is known to reduce screen brightness while playing music, especially if you are not looking at your device or if your device senses that it is not being used.
While this problem is more commonly reported by iPhone Mini users, you can try to switch music ON/OFF on your device and see if this is true in your case.
6. Disable Low Power Mode
In Low Power Mode, iPhone reduces screen brightness to save battery life. If you are using Low Power Mode to conserve battery life, you can manually disable this feature.
Go to Settings > Battery > move the slider next to Low Power Mode to OFF position.
Note: If your Battery is low in Power, it can quickly run out of Power when Low Power Mode is manually disabled.
7. Check Auto-Brightness
Lastly, make sure that you have not accidentally enabled the Auto-Brightness feature on your device.
Go to Settings > Display & Brightness > move the toggle next to Automatic to OFF position.
Note: Turning OFF Auto-Brightness can have an adverse impact on battery life. You can counter this by keeping your device at a reasonable brightness level (Not too High or Low).